In reality, there are only 3 separate connections:
The 4th physical pin is electrically the same as the output pin.
In your schematic symbol, create one with only 3 pins, and assign the correct name to the correct pin number. It would be good practice to organize the symbol pins by function from left to right, and not numerically from lowest to highest.
Later when you assign a footprint to the symbol, that footprint will have 4 physical pins. However, one of the pins will have one of the pin names the same as the first instance of "output" (as this is the pin that is duplicated on this particular part).
The symbol will have these pins and names:
Pin 1) Adjust
Pin 2) Output
Pin 3) Input
The footprint will have 4 physical pins, one with the same name:
Pad 1 will be pin 1 of the symbol.
Pad 2 will be pin 2 of the symbol.
Pad 3 will be pin 3 of the symbol.
Pad 4 (or the tab) will also be assigned to pin 2 of the symbol.
You can open the footprint browser and check out TO_SOT_Packages_SMD:SOT-223-3Lead_TabPin2 for an example.
Hope this helps.